The field of the present invention is four-wheel drive vehicles of the type where the rider straddles the vehicle, and more specifically frame structures therefor.
Four-wheel drive vehicles have been developed employing a central frame structure with front and rear driven wheels. The central frame structure of such vehicles generally include an upper frame and a lower frame with a seat located on the upper frame and the engine between the frames. Such devices have found application to off-road riding for utilitarian and recreational purposes.
An advantageous feature to have on such vehicles is a relatively small turning radius. With a small turning radius, insurmountable objects in the terrain can be circumvented with greater facility. In addition, the frame structures of such vehicles must be relatively substantial in order to sustain the loads experienced in off-road use, particularly from tilting of the axle relative to the vehicle. However, such substantial structures generally have restricted the pivoting of the front wheels of such vehicles, increasing the minimum turning radius. Consequently, the structural requirements of such vehicles tend to interfere with their maneuverability.